The invention relates to a propelling nozzle for aircraft equipped with jet engines, and particularly for lateral thrust vector control.
Under the name of "Stealth Bomber B-2", an aircraft which is to be largely insensitive to radar and infrared detection is known, for example, from the German Publication DE-Z Fluo Revue, No. 1, January 1988. For the predominant part, the aircraft consists of a relatively far projecting wing unit with fuselage as well as pay load receiving structures integrated into it. For this purpose, by means of tunnel-type air inlets projecting out of the top sides of the wing surfaces, fanjet engines are to be supplied with air which are arranged in the wing structure in a physically inwardly and downwardly retracted manner. In other words, the known case involves a subsonic aircraft concept also because, in order to limit heat emissions resulting from the thrust jet, the thrust jet is a mixture of a hot core jet, relatively high parts of fan air -and additionally taken-in boundary layer air. This is in contrast to conventional aircraft which are designed for supersonic flight, are constructed as combat aircraft or as arms carriers and can be detected relatively easily by, among other devices, infrared sensors, and in the case of which often gas turbine jet engines with a relatively low bypass flow ratio are used in combination with an afterburning system (afterburner) which can be switched on, for example, for the supersonic flight operation.
From the German Patent Document DE-PS 11 44 117, a jet deflection arrangement is known which can be used, in particular, for vertical take-off aircraft and which consists of pipe bend segments which can be pivoted in a telescopic manner, in combination with an additional jet directing cascade that is situated in the pipe bend segment which can be moved the farthest to the outside and that consists of rotary blades which can each be pivoted simultaneously about respective central axes. The remaining jet deflection which is the result of such a jet directing cascade construction and arrangement is connected with a still considerable throttling effect as well as deflecting losses of the exhaust gas jet with the corresponding repercussions on the engine. The telescopic movability of the pipe bend segments is comparatively complicated and not free of susceptibility to trouble (thermally caused pipe warping). Also, in the known case, a response action for a thrust vector control should be expected that is relatively slow with respect to time.
From the German Patent Document DE-GM 70 08426, a thrust jet coupling arrangement is known in which deflecting blades arranged in the manner of a deflecting cascade are to each consist of a fixed inlet section and individual sections which can be pivoted on it continuously in order to thus try to eliminate the disadvantage of the already discussed throttling effect on the engine. It is a prerequisite for the implementability of the known case that corresponding multi-member deflecting blades with their respective first rotating shafts are arranged in the area of a diagonally cut outlet plane of a housing wall end. With respect to an axially symmetrical oncoming flow, no jet deflection or thrust vector control is possible in the known case which takes place on both sides of this oncoming flow in a plane, that is, toward one direction and to a direction that is opposite to it. On the whole, between the deflecting blades, no constant outlet cross-section or narrowest cross-section in the sense of a "convergent nozzle", which always accelerates the flow, is made available in the outlet plane. The adjusting expenditures and the degree of susceptibility to disturbances with respect to linkages between the individual blade segments are relatively high.
A propelling nozzle according to the initially mentioned type is known from the U.S. Pat. No. 3,640,469. In this known case, it is assumed that three flaps exist which are arranged at the same mutual distance in the plane containing the axes of rotation. In this case, the three flaps are to be actuated by way of a comparatively complicated multiple lever and link arrangement which partly operates in a manner of a gearing. In this case, each outer flap is non-rotatably connected with a separate actuating lever extending in the longitudinal direction of the flap. At the respective rearward end, the actuating levers are coupled with the one end of links. At the other end, these links are pivotally coupled at an upstream point with a rocking lever which is pivotable about a downstream housing point. At an arm, which laterally projects out of the rocking lever and is fixedly connected with it, one end of another swivel arm is to be linked which is coupled by means of its other end to the downstream end of another actuating lever. At its other end, this actuating lever is non-rotatably connected with the center flap of the propelling nozzle on the side of the axis of rotation. In the known case, the adjusting force is to be introduced approximately in parallel to the nozzle axis into the laterally projecting arm of an actuating lever (double-armed lever) which is part of an outer nozzle flap. In the known case, while all flaps are controlled simultaneously, a torsion of the rocking lever takes place which is converted to a central differential-angle control of the center flap with respect to the outer flaps. In the known case, it is virtually not possible to be able to control either only two (outer) flaps or more than three flaps in a blade cascade-type manner, in each case, by different torsional angles. The reason is that, particularly in the latter case, it is necessary to be able to locally control larger or smaller thrust jet deflections between two adjacent flaps. In the interest of locally reduced deflecting losses (locally relatively abrupt deflection by way of two flaps of the cascade), it is therefore required to make available correspondingly larger dimensioned local nozzle surface cross-sections and, at the same time, in turn, maintain the required nozzle convergence between two flaps. For this purpose, the known case furnishes no tangible starting point to a solution because it aims exclusively at a constant-surface convergent nozzle construction along the whole deflecting range in the case of thrust vector control. In addition, in the known case, by means of the above-described gearing-type control lever configuration (different lengths of the additional swivel arm and of the additional actuating lever: in this case, center flap), while the flaps are controlled at the same time, deflecting angles of various sizes of the center flap are obtained, while it is pivoted toward the one or toward the other side as well as relatively with respect to the control positions of the two outer flaps, so that the laws endeavored in the known state of the art (keeping the outlet surface constant) cannot be carried out in practice. In other words, the individual degree of freedom for a locally varying flap pivoting is estimated to be very low. The latter applies particularly if the thrust-vector control of the air exhaust gas systems of several engines by means of a cascade-type nozzle system is involved. In addition, in the known case, in view of the flap control, relatively large stress moments are to be expected which affect the control system. Also, the known case can probably be implemented only by means of relatively thick-walled and heavy flaps which have a shape that tapers in a wedge shape from the direction of the respective pivot bearings. In the known case, the total of the control device expenditures is relatively high which is accompanied by an increase in weight.
The above-discussed known nozzle or jet deflecting concepts provide no information concerning a development and an arrangement with respect to a reduced radar and/or infrared detection. These known deflecting concepts also do not concern the problem of processing, in each case, the thrust jets of two or several jet engines in the manner of nozzles and for the purpose of a 2-dimensional thrust vector control in such a manner that, on the nozzle side, a risk of being detected by radar or infrared detection is as low as possible.
The invention is based on the object of providing a controllable propelling nozzle which is suitable for an initially mentioned type of aircraft and which permits a 2-dimensional thrust vector control, while the flap control is as fast as possible, with relatively low control device expenditures, without causing in variable positions impermissible deflecting losses and throttling of one or several exhaust gas flows.
The mentioned object is achieved by a propelling nozzle for aircraft equipped with jet engines, particularly for the lateral thrust vector control, in the case of which at least two flaps actuated by way of lever-type control members are arranged at their upstream ends to be pivotable about pivots extending transversely with respect to the nozzle axis, said flaps being disposed as well between walls of a square nozzle housing extending essentially in parallel to the nozzle axis, said flaps being simultaneously pivotable about different twisting angels in such a manner that--while the nozzle contour course is always convergent--an exit-side narrowest cross-section is formed between the flaps, characterized in that the ends of one side of the lever-type control members are applied to downstream flap ends, the control members being arranged at the level of their other ends movably coupled with one anther so that they can be moved in a track which is connected to be curved for simultaneously always forcing different flap twisting angles.
The invention permits the providing of a nozzle concept, which is convergent in all flap positions, and by means of which exhaust-gas fan air jet mixtures delivered by one or several engines, particularly for the purpose of a variable lateral control of an airplane, can be carried through with extremely low aerodynamic losses. In the area of the fuselage end and/or the wing end, particularly in the case of an aircraft of the initially mentioned type, the propelling nozzle may be constructed to be extremely flat (low installation height) and, because of the comparatively short flap lengths, can be constructed to be comparatively short, which, in turn, has a favorable effect with respect to a comparatively light weight of the nozzle.
In the case of the present propelling nozzle, it is therefore ensured that the geometrically narrowest cross-section which can be adjusted in each case between two flap ends according to the requirements, is situated at the nozzle end and --while avoiding deflecting losses--no flow-through changing repercussions occur on the inside nozzle flow which, in turn, could endanger the engine operation. Even with only two flaps, it is possible to either make available an always convergent nozzle with an always constant narrowest cross-section or an always convergent nozzle with a nozzle surface cross-section or narrowest cross-section which increases as a function of an increasing jet deflecting angle.
According to the invention, advantageously a blade cascade-type multiple flap nozzle may be provided in the case of which a medium or central nozzle flap defines the required or nominal or maximal jet deflecting angle. In view of the after expansion of the carried-through gas flows behind the respective narrowest nozzle cross-section, a possibly resulting slight reduction of the required jet deflection can be compensated by a more pronounced angular incidence of outer flaps relative to the position of the corresponding center nozzle flap.
The designability of the propelling nozzle (flat long-drawn-out rectangular cross-section) which, particularly when several nozzle flaps are used, in a blade cascade-type manner, is extremely flat, reduces the danger of detection with respect to infrared sensors, particularly in combination with an--according to the invention--backwardly and downwardly sloped nozzle outlet or with respect to the inclined installing position of the engine or engines in the or on the aircraft.
The propelling nozzle according to the invention may also be used for the jet deflection or the thrust jet pivoting in a vertical or perpendicular plane, for example, in the case of two jet engines arranged above one another.
Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.